Unit Vector

Description:

• In ${\mathbb{R}}^n$, the $i$-th unit vector is the $n$-vector $e_i$ such that all entries are 0 except the $i$-th
  • example, $e_2$ of ${\mathbb{R}}^4=$ $\left(\begin{array}{c}0\\ 1\\ 0\\ 0\end{array}\right)$